Hydraulic braking energy utilization for emergency steering, braking, charging accumulator(s), and/or work functions to reduce or prevent engine from overspeed, assist acceleration and/or unlimited towing

ABSTRACT

A system and method configured to direct the braking energy from a high-pressure port at the motor side of a hydraulic circuit to emergency steering, braking, accumulator(s) charging, and/or various work functions. The system and method are also configured to return hydraulic fluid back to the same high-pressure port when the motor is running as a pump.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation of U.S. application Ser. No.17/350,799 filed Jun. 17, 2021, which in turn is a continuation of U.S.application Ser. No. 16/184,195 filed Nov. 8, 2018, which in turn claimspriority on United States Application Ser. No. 62/583,298 filed Nov. 8,2017, which are incorporated herein by reference.

The present disclosure is directed to a system and method configured todirect the braking energy from a high-pressure port at a propulsionmotor side of a hydraulic circuit/system and to at least partially usesuch energy for (a) emergency steering and braking; (b) input intoaccumulator(s); and/or, (c) various other work functions. Moreover, thesystem and method of the present disclosure is configured to returnhydraulic fluid (e.g., hydraulic fluid, etc.) back to the same port atthe propulsion pump side when the motor is running as a pump. The motormay run as a pump, for example: (1) when the engine dies at high machinevelocity on flat ground; (2) when the engine dies while the machinetravels downhill; (3) during machine deceleration; and/or, (4) when themachine is being towed.

BACKGROUND

Systems and methods for controlling speed and braking in vehicles havinghydrostatic drives are known in the art. During braking in some knownhydrostatic drives, an associated motor gathers the vehicle's momentumand runs as a pump, while an associated pump runs as a motor. The inputtorque from the pump transfers to the vehicle's engine and can causeoverspeed due to insufficient engine braking power. The more inputtorque, the more engine overspeed, and/or excessive overspeed can resultin damage to the engine and the pump.

During braking in other known hydrostatic drives, a speed limitercircuit is utilized which converts excessive hydrostatic power to heatthrough a pressure-reducing valve. The heat energy is then dissipated tothe ambient environment through the transmission housing or via anassociated hydraulic fluid cooler. While this approach provides engineoverspeed protection to a certain level, the heat energy dissipated tothe ambient environment reduces overall system performance andefficiency. Examples of prior art speed control and hydrostatic drivesare disclosed in U.S. Pat. Nos. 9,512,918 and 7,874,153, which areincorporated herein by reference.

Systems and methods for overcoming these prior art deficiencies relatedto speed and braking control in vehicles having hydrostatic drives areneeded.

BRIEF DESCRIPTION

Non-limiting aspects of the present disclosure include a system andmethod configured to direct the braking energy in a propulsion circuitof a machine. More particularly, the braking energy is directed from ahigh-pressure port at the propulsion motor side of the circuit to beused in: (a) an emergency steering and braking circuit; (b) one or moreaccumulators; and/or (c) any other work functions performed by commoncomponents in machines which utilize propulsion circuits.

Moreover, in accordance with other non-limiting aspects of the presentdisclosure, the exemplary system and method are configured to returnhydraulic fluid back to the same high-pressure port at the propulsionpump side when the motor is running as a pump. This may occur, forexample, when: (1) the engine dies at high machine velocity on flatground; (2) the engine dies while the machine is undergoing downhilltravel; (3) the machine is decelerating; (4) the machine is being towed;and/or, (5) any other time the propulsion motor is being driven as apump. Thus, the system and method of the present disclosureadvantageously utilize braking energy to overcome the aforementioneddeficiencies of the prior art.

In some non-limiting embodiments, braking energy can first be utilizedfor emergency steering and braking operations. In other non-limitingembodiments, braking energy can also or alternatively be stored inaccumulators for later use. In additional non-limiting embodiments,braking energy can also or alternatively be utilized in any number ofdifferent types of work functions commonly performed by machines whichutilize propulsion circuits. For example, braking energy can be at leastpartially utilized in different work functions to: (a) minimize heat(e.g., by avoiding the use of a pressure-reducing valve to dissipate theenergy); (b) minimize engine overspeed (e.g., by reducing the pump sidepressure at port B to a level that results in minimum input torquetransferred to the engine); (c) assist in machine acceleration; (d)enable unlimited towing; and/or (e) limit steering during towing.

One non-limiting object of the present disclosure is to provide ahydraulic circuit which includes a pump configured to be driven by aprime motor. The circuit further includes a hydrostatic motor fluidlycoupled to the pump by first and second lines (i.e., supply and returnlines), one or more work function actuators or accumulators fluidlycoupled with at least one of the first and second lines, and valvingoperative to direct at least a portion of pressurized fluid output fromthe motor during braking operations to at least one of the one or morework function actuators or accumulators. These exemplary non-limitingcomponents thereby reduce or prevent the prime motor (i.e., engine) fromover-speeding, as well as minimize heat generation in the hydrauliccircuit.

The non-limiting hydraulic circuits disclosed herein can optionallyfurther include a pressure-reducing valve for converting hydraulicenergy to thermal energy, wherein the valving is further operative todirect pressurized fluid from the motor to the pressure-reducing valveduring braking. Over-speeding in the prime motor is thereby prevented.

In accordance with other non-limiting aspects of the present disclosure,the exemplary hydraulic circuit is optionally at least one of ahydrostatic or open machine propel circuit. The hydrostatic propelcircuit optionally includes a plurality of motors and pumps, and theplurality of motors include at least one of a fixed, 2-position, orproportional motor. The open-circuit propel system optionally includes aplurality of motors and one pump, and the plurality of motors include atleast one of a fixed, 2-position, or proportional motor.

In accordance with other non-limiting aspects of the present disclosure,the one or more work function actuators optionally can include at leastone work motor of a fan drive motor, a generator motor, cylinders,rotary actuators, or any motor that is loaded during engine dynamicbraking. The work motor can be part of a fixed or variable pump system,open-circuit or closed-loop hydrostatic system. The hydraulic circuitoptionally further includes a work function pump configured to bede-stroked to zero displacement, or dump its output to a reservoir,during engine dynamic braking. The hydraulic circuit optionally furthercomprises a micro-controller. The hydraulic circuit can optionally beused in a hydrostatic drive of a machine for propelling the machine.

In accordance with other non-limiting aspects of the present disclosure,there is provided a method of controlling a hydraulic drive of amachine, the hydraulic drive including a pump adapted to be driven by aprime motor of the machine, a motor fluidly coupled to the pump by firstand second lines for propelling the machine, and at least one of a workfunction actuator or an accumulator fluidly coupled with at least one ofthe first and second lines. The method includes, during machinedeceleration, directing at least a portion of pressurized fluid outputfrom the motor to at least one of the work function actuator or theaccumulator to thereby prevent the prime motor from over-speeding and tominimize heat generation in the hydraulic circuit.

In accordance with other non-limiting aspects of the present disclosure,there is provided a hydraulic circuit that uses the braking energy of ahydrostatic propulsion system for: (a) emergency steering; (b) braking;(c) charging accumulator(s); (d) one or more work functions to preventthe engine from overspeed and minimize heat generation; (e) assistingacceleration; and/or (f) unlimited towing when the propulsion motor isrunning as a pump. The hydraulic circuit is optionally at least one ofthe hydrostatic or open-circuit propulsion systems. The hydrostaticpropel circuit optionally includes a plurality of motors and pumps,wherein the plurality of motors include at least one of a fixed orvariable motor. The open-circuit propel system optionally includes onepump and a plurality of motors, and wherein the motors include at leastone of a fixed or variable motor. The accumulator can optionally be astandalone component, or in a charging system with a fixed or variablepump. The normal steering and braking system optionally has a fixed orvariable pump.

In accordance with other non-limiting aspects of the present disclosure,the work function actuator can optionally include at least one workmotor of a fan drive motor, a generator motor, cylinders, rotaryactuators, or any motor that is loaded during engine dynamic braking,and wherein the work motor can be part of a fixed or variable pumpsystem.

In accordance with other non-limiting aspects of the present disclosure,the hydraulic circuit optionally further includes a work function pumpconfigured to be de-stroked to zero displacement, or dump its output toa reservoir, during engine dynamic braking.

In accordance with other non-limiting aspects of the present disclosure,the hydraulic valve manifold that directs the braking energy to all thefunctions optionally includes any type of hydraulic valve and/orsolenoid valve. The braking energy is optionally from the high pressureat the propel motor side when the motor is running as a pump. The motormay run as a pump, for example, when: (a) the engine dies at highmachine velocity on flat ground; (b) the engine dies while travellingdownhill; (c) the machine is decelerating; and/or, (d) the machine isbeing towed in forward direction.

In accordance with other non-limiting aspects of the present disclosure,the braking energy can also optionally be from the high pressure at thepropel motor side when the motor is running as a pump and the port B(e.g., return line) is blocked between the motor and the pump. Inaddition, the braking energy can optionally be from pressure at port Bon the propel motor side if port A is high pressure when the machinetravels forward direction. Furthermore, the braking energy can alsooptionally be from pressure at port A on the propel motor side if port Bis high pressure when the machine travels in a forward direction. Thehydraulic circuit optionally further comprises a micro-controller.

In accordance with other non-limiting aspects of the present disclosure,a hydraulic circuit is disclosed which includes a pump configured to bedriven by a prime motor, a motor fluidly coupled to the pump by a supplyline and a return line, at least one work function circuit fluidlycoupled with at least one of the supply and return lines, and valvingoperative to direct at least a portion of pressurized fluid output fromthe motor during braking operations to the at least one work functioncircuit to thereby reduce or prevent the prime motor from over-speedingand/or to minimize heat generation in the hydraulic circuit.

In accordance with other non-limiting aspects of the present disclosure,the hydraulic circuit can optionally be a hydrostatic and/or openmachine propel circuit.

In accordance with other non-limiting aspects of the present disclosure,the at least one work function circuit can optionally further include atleast one of a work motor and/or a work function pump.

In accordance with other non-limiting aspects of the present disclosure,the work motor can optionally include one of a fan drive motor, agenerator motor, cylinders, and/or rotary actuators.

In accordance with other non-limiting aspects of the present disclosure,the work function pump can optionally be configured to be de-stroked tozero displacement and/or to dump its output to a reservoir.

In accordance with other non-limiting aspects of the present disclosure,the hydraulic circuit can optionally further include one or moreaccumulators configured to be charged by the at least one work functioncircuit.

In accordance with other non-limiting aspects of the present disclosure,the accumulator can optionally be a standalone component or be includedas part of a charging system having a fixed and/or variable pump.

In accordance with other non-limiting aspects of the present disclosure,the at least one work function circuit of the hydraulic circuit canoptionally include an engine control circuit configured to minimizeover-speeding in the prime motor, assist in acceleration, and/or permitunlimited towing.

In accordance with other non-limiting aspects of the present disclosure,the engine control circuit can optionally include one or more solenoidvalves, an orifice, a pressure relief valve, one or more pressuretransducers, one or more hydraulic pilot-operated valves, a check valve,a pressure-reducing valve, and combinations thereof.

In accordance with other non-limiting aspects of the present disclosure,the at least one work function circuit of the hydraulic circuit canoptionally include a heat control circuit configured to minimize heatgeneration.

In accordance with other non-limiting aspects of the present disclosure,the heat control circuit can optionally have a fan pump and/or a fandrive motor.

In accordance with other non-limiting aspects of the present disclosure,the at least one work function circuit of the hydraulic circuit canoptionally further include a braking energy circuit configured tocontrol emergency steering and/or braking.

In accordance with other non-limiting aspects of the present disclosure,the braking energy circuit can optionally have a steering circuitcontrol, a braking circuit control, and/or a hydraulic valve manifoldconfigured to direct braking energy.

In accordance with other non-limiting aspects of the present disclosure,there is provided a hydrostatic propulsion system in a machine. Thesystem includes a hydraulic circuit which can have a pump configured tobe driven by an engine, a motor fluidly coupled to the pump by a supplyline and a return line, the motor including a high-pressure port sideand being configured to run as a pump. The system can also include apressurized fluid output from the motor during a deceleration of themachine and at least one work function circuit fluidly coupled with atleast one of the supply and return lines. The at least one work functioncircuit can include an engine control circuit configured to minimizeover-speeding in the engine, assist in acceleration, and/or permitunlimited towing. The high-pressure port side of the motor can beconfigured to direct a braking energy generated from the deceleration tothe at least one work function circuit.

In accordance with other non-limiting aspects of the present disclosure,the system can optionally further include one or more operatingconditions in which the motor runs as a pump. The one or more operatingconditions include, but are not limited to: the engine dying when themachine is operating at a high velocity on flat ground; the engine dyingwhen the machine is travelling downhill; machine deceleration; themachine is being towed in a forward direction; a port of the return linebeing blocked between the motor and the pump; and/or the machine istraveling in a forward direction.

In accordance with other non-limiting aspects of the present disclosure,the at least one work function circuit of the system can optionallyfurther include a heat control circuit configured to minimize heatgeneration.

In accordance with other non-limiting aspects of the present disclosure,the at least one work function circuit can optionally include a brakingenergy circuit configured to control emergency steering and/or brakingand which can include one or more accumulators.

In accordance with other non-limiting aspects of the present disclosure,there is provided a method of controlling a hydraulic drive of amachine. The hydraulic drive includes a pump adapted to be driven by anengine of the machine, a motor fluidly coupled to the pump by a supplyline and a return line and including a high-pressure port side, and atleast one work function circuit fluidly coupled with at least one of thesupply and return lines. The method can include directing at least aportion of a pressurized fluid output from the high-pressure port sideof the motor to the at least one work function circuit and, returningthe pressurized fluid back to the high-pressure port side of the motorwhen the motor is running as a pump; wherein the directing and returningprevents over-speeding in the prime motor and/or minimizes heatgeneration in the hydraulic drive.

In accordance with other non-limiting aspects of the present disclosure,the method can optionally further include one or more of: assisting inaccelerating the machine; permitting unlimited towing of the machine;emergency steering and braking of the machine; and/or charging one ormore accumulators. The assisting of the accelerating, the permitting ofthe unlimited towing, the emergency steering and braking, and/or thecharging of one or more accumulators is being performed by the directingof the pressurized fluid to the at least one work function circuit.

In accordance with other non-limiting aspects of the present disclosure,the returning of the pressurized fluid back to the high-pressure portside of the motor when the motor is running as a pump can optionallyoccur when the engine dies while the machine is operating at a highvelocity on flat ground, the engine dies while the machine is travellingdownhill, the machine decelerates, the machine is being towed in aforward direction, a port of the return line is blocked between themotor and the pump, and/or the machine is traveling in a forwarddirection.

These and other objects and advantages will become apparent from thediscussion of the distinction between the present disclosure and theprior art and when considering the non-limiting embodiments of thedisclosure as shown in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference may now be made to the drawings, which illustrate variousembodiments that the disclosure may take in physical form and in certainparts and arrangements of parts wherein:

FIG. 1 is a schematic diagram of an exemplary prior art hydrostaticpropel system with one pump and one motor;

FIG. 2 is a schematic diagram of an exemplary prior art hydrostaticpropel system with a speed limiter for engine overspeed protection;

FIG. 3A is a schematic diagram of an exemplary hydrostatic propel systemwith braking energy recovery/use for emergency steering, braking,charging accumulator(s), work functions to prevent engine fromoverspeed, assisting acceleration, and/or unlimited towing in accordancewith the present disclosure;

FIG. 3B is a portion of the exemplary hydrostatic propel system of FIG.3A which specifically shows a schematic diagram for a braking energycircuit to recover/use braking energy for the emergency steering,braking, and charging accumulator(s);

FIG. 4A is a schematic diagram of an exemplary hydrostatic propel systemin accordance with the present disclosure for engine overspeedprotection including a fan drive motor in an electronic diesel control(“EDC”) pump system;

FIG. 4B is a simplified version of the schematic diagram of FIG. 4A;

FIG. 5 is a schematic diagram of an exemplary hydrostatic propel systemin accordance with the present disclosure for engine overspeedprotection, including a hydraulic fan drive motor in a fixeddisplacement pump system;

FIG. 6A is a schematic diagram of an exemplary hydrostatic propel systemin accordance with the present disclosure for engine overspeedprotection, including an accumulator charging system and emergencysteering and braking; and,

FIG. 6B is a portion of the exemplary hydrostatic propel system of FIG.6A which specifically shows a schematic diagram for a braking energycircuit to recover/use braking energy for the accumulator chargingsystem and emergency steering and braking.

DETAILED DESCRIPTION OF NON-LIMITING EMBODIMENTS

Referring now in greater detail to the drawings, wherein the showingsare for the purpose of illustrating non-limiting embodiments of theinvention only and not for the purpose of limiting the invention, FIG. 1illustrates a typical prior art closed-loop hydrostatic propulsionsystem 100. The system 100 generally includes a hydrostatic pump 104fluidly coupled to one or more hydrostatic motor(s) 112 forming a mainhydraulic loop 120. The hydrostatic motor(s) 112 can be fixed orvariable. The pump 104 is typically connected to a prime motor 102, suchas an internal combustion engine or the like, of a machine or vehicle.The prime motor 102 drives the pump 104 to deliver hydraulic fluid tothe motor 112 via supply/return lines 110/118. The motor 112 drives oneor more wheels, tracks, etc. to propel the vehicle.

A valve 114 (electric proportional/on-off, or hydraulicproportional/on-off, or manual proportional/on-off, or non-servo directdisplacement control) inside the pump 104 controls the speed anddirection of the motor 112 by modulating flow rate and changing flowdirection supplied to the motor 112 by the pump 104. A charge pump 106replenishes the main hydraulic loop 120 with cool and clean hydraulicfluid from a sump (reservoir) 122. High pressure relief valves 108/116provide overpressure protection for the main hydraulic loop. The machineis designed to travel forward when port A of the motor 112 and the pump104 is high pressure, and travel in reverse when port B of the motor 112and the pump 104 is high pressure.

When moving in a forward direction and the machine begins to decelerate(i.e., when the machine shifts to a “braking mode”), pump 104 de-strokestoward 0 degrees and Port A pressure drops, and port B pressureincreases. In braking mode, the motor 112 gathers the vehicle's momentumand runs as a pump, while pump 104 runs as a motor. The input torquefrom the pump 104 transfers to the prime motor 102 (i.e., the machine'sengine) and can cause overspeed in the engine due to insufficient enginebraking power. The more input torque, the more engine overspeed.Excessive overspeed may damage the engine 102 and the pump 104.

Higher pressure on port B at the motor 112 side provides sufficientbraking torque to stop the machine. Lower pressure on port B at the pump104 side reduces the input torque from the pump 104 to the engine andavoids excessive engine overspeed.

There is typically little or no engine overspeed risk during machinedeceleration when operating in the reverse direction because the maximumreverse speed is normally much slower.

FIG. 2 illustrates a prior art closed-loop hydrostatic system 200 with asimilar configuration to the hydraulic circuit 100 of FIG. 1 . That is,the closed-loop hydrostatic propulsion system 200 of FIG. 2 includes ahydrostatic pump 204, a main hydraulic loop 228, and one or morehydrostatic motor(s) 212. The pump 204 is connected to the prime motor202 of a machine or vehicle. The prime motor drives the pump 204 todeliver hydraulic fluid to the motor 212 via supply/return lines210/218. A valve 214 inside the pump 204 controls the speed anddirection of the motor 212 by modulating flow rate and changing flowdirection supplied to the motor 212 by the pump 204. A charge pump 206replenishes the main hydraulic loop 228 with cool and clean hydraulicfluid from a sump (reservoir) 232. High pressure relief valves 208/216provide overpressure protection for the main hydraulic loop.

The prior art closed-loop hydrostatic system 200 illustrated in FIG. 2differs from system 100 of FIG. 1 in that the main hydraulic loop 228includes a speed limiter circuit 230 for preventing engine overspeed.The speed limiter circuit 230 includes a pilot pressure relief valve220, a bypass orifice 222, and a pressure-reducing valve 226. Excessivehydrostatic power is converted to heat by the pressure-reducing valve226. The heat energy is then dissipated to the ambient environmentthrough the transmission housing or via an associated hydraulic fluidcooler. Bypass check valve 224 is for free flow when the machine travelsin reverse.

During operation of a machine which utilizes a closed-loop hydrostaticsystem having a speed limiter circuit, such as system 200 and speedlimiter circuit 230 illustrated in FIG. 2 , the speed limiter circuitfunctions to automatically limit the pump torque input to the engine.This may occur when, for example, the pump 204 is being driven as amotor during vehicle deceleration. Accordingly, when the system 200 isin braking mode, the hydrostatic motor side may have a port B pressureof about 510 bar, for example. The speed limiter circuit 230 could thenfunction to limit the pump side pressure of port B to some lowerpressure such as about 170 bar, for example.

Non-limiting aspects of the present disclosure are directed to a system(and method) that uses the braking energy of a hydraulic propel systemfor emergency steering, braking, and/or charging accumulator(s) when theengine dies at high machine velocity on flat ground, when the enginedies while the machine travels downhill, for work functions to minimizeheat generation and engine over-speed during machine deceleration, forassisting acceleration, and/or for unlimited towing and limited steeringduring towing.

Non-limiting aspects of the present disclosure can be used in connectionwith a wide range of hydraulic circuits to direct braking energy to runemergency steering, braking and/or charge accumulator(s) in the eventthe prime motor (engine) dies. Certain non-limiting embodiments includepropel systems with one or pumps and one or more motors. The motor(s)can be fixed and/or variable.

Non-limiting aspects of the present disclosure can be implemented in awide variety of hydraulic drive systems or other hydraulic circuits andmethods. In particular, certain aspects are directed to circuit designsthat direct braking energy to any type of work function actuators (e.g.,cylinders, rotary actuators, etc.) that are loaded, such as a fan motorand/or a generator motor, etc. in a fixed or variable pump system,open-circuit or closed-loop hydrostatic. The work function pump (ifpresent) either dumps its output to a reservoir or de-strokes to 0degrees during machine deceleration.

Non-limiting aspects of the present disclosure can be implemented in awide variety of hydraulic circuit designs and, in particular, certainaspects are directed to circuit designs wherein a valve manifold directsthe braking energy to functions using any type and/or combination ofhydraulic valves and/or solenoid valves.

Referring now to FIGS. 3A and 3B, an exemplary hydraulic circuit 300 inaccordance with the present disclosure is illustrated. The exemplaryhydraulic circuit 300 generally includes a hydrostatic pump 304 and oneor more hydrostatic motor(s) 312. The pump 304 is connected to a primemotor (not shown) of a machine or vehicle. The prime motor of a machineor vehicle as disclosed herein may be, for example, a hydrostatictransmission of the hydrostatically-driven vehicle such as, for example,a forklift truck or construction machinery. However, this aspect isnon-limiting and other types of vehicles or machines can be used withexemplary hydraulic circuit 300. The prime motor drives the pump 304 todeliver hydraulic fluid to the motor 312 via first and second lines(i.e., supply/return lines 310/318).

In the embodiment illustrated in FIGS. 3A and 3B, the braking energy isutilized for emergency steering, braking, charging accumulator(s),and/or one or more of work functions (hydraulic actuators) to minimizeheat generation, minimize engine overspeed, assisting accelerationand/or assisting unlimited towing. More particularly, circuit 300includes one or more dedicated work function circuits configured toperform one or more of the aforementioned tasks. Generally, eachdedicated work function circuit can include one or more work functionactuators and/or one or more work function pumps. The function actuatorsare typically a work motor; however, such a configuration isnon-limiting. Exemplary work motors include but are not limited to fandrive motors, generator motors, cylinders, rotary actuators, and/or anymotor that is loaded during engine dynamic braking.

In one non-limiting configuration, hydraulic circuit 300 includes a workfunction circuit 319 configured to minimize engine overspeed, assist inacceleration, and permit unlimited towing (i.e., engine control circuit319). As illustrated in FIG. 3A, the engine control circuit 319generally includes one or more solenoid valves 320/338, orifice 322,relief valve 324, one or more pressure transducers 326/328, one or morehydraulic pilot-operated valves 330/332, check valve 334, and pressurereducing valve 336. However, such a configuration is non-limiting.

In another non-limiting configuration, hydraulic circuit 300 can furtherinclude work function circuit 339 configured to minimize heat generation(i.e., heat control circuit 339). As illustrated in FIG. 3A, the heatcontrol circuit 339 is generally a fixed displacement pump system thatincludes fan pump 340, solenoid valve 342, check valve 344, fan drivemotor 346, and 4-way valve 348. However, such a configuration isnon-limiting.

In additional non-limiting configurations, hydraulic circuit 300 canalso include a braking energy circuit 349 configured to controlemergency steering and braking as well as accumulator(s) charging. Asillustrated in FIG. 3B, the braking energy circuit 349 generallyincludes steering control circuit 350, braking control circuit 352,solenoid valve 354, accumulator(s) 356, and hydraulic valve manifold358. However, such a configuration is non-limiting. The steering controlcircuit 350 and braking control circuit 352 can optionally include oneor more fixed or variable pumps. The hydraulic valve manifold 358 of thebraking energy circuit 349 typically includes any number of differenttypes of hydraulic valves and/or solenoid valves which can be configuredto direct the braking energy to each of the dedicated work functions,such as charging accumulator(s) 356, enabling steering and braking bycontrol circuits 350/352, powering heat control circuit 339, andenabling engine control circuit 319. However, such a configuration isnon-limiting.

Moreover, the hydraulic circuit 300 and each of the dedicated workfunction circuits (e.g., engine control circuit 319, heat controlcircuit 339, braking energy circuit 349) include valving (shown but notnumbered) which is generally operative to direct at least a portion ofpressurized fluid output from the motor during braking operations to atleast one of the one or more work function circuits or accumulators. Itshould also be appreciated that other types of work functions canadditionally or alternatively be powered by the braking energy withoutdeparting from the scope of this disclosure.

The exemplary hydraulic circuit 300 illustrated in FIGS. 3A and 3B isadvantageously enabled to respond to various states of machineoperation. For example, exemplary hydraulic circuit 300 may operate inresponse to machine operation states such as: when the engine dies athigh machine velocity on flat ground; when the engine dies while themachine travels downhill; during machine deceleration; when the machineis being towed; and/or any other situation when motor 312 is running asa pump and the pump 304 is running as a motor. During these situations,port B pressure goes up, and port A pressure goes down. The hydraulicpilot-operated valves 330 and 332 shift when port B pressure reaches acertain predetermined value (e.g., 50 bar, 75 bar, 45 bar, etc.). Byblocking port B between the pump 304 and the motor 312, the brakingenergy from high-pressure port B at the motor 312 side is transferred tothe various other work functions (e.g., transferred to run steering,braking, charging accumulator(s), etc.).

During operation of exemplary hydraulic circuit 300, thepressure-reducing valve 336 setting determines the pressure to which theaccumulator 356 is charged. When the accumulator 356 is fully charged,the micro-controller (not shown) receives a signal from the pressuretransducer 328 and energizes the solenoid valves 342 and 338. The fanpump 340 dumps hydraulic fluid to reservoir 360 via solenoid valve 342.The braking energy is directed to run the fan motor 346 via a 4-wayvalve 348. The check valve 344 blocks fluid from back flowing into thefan pump 340.

The exemplary micro-controller (not-shown) described herein can includea processor for operating software logic and can be connected to aplurality of sensors which detect various characteristics of thehydraulic circuit. For example, sensors can be positioned to detectengine load, system speed, differential pressures, etc.

The return hydraulic fluid from the fan motor 346 goes back to port B atthe pump 304 side and/or the reservoir 360. This minimizes input torquefrom the pump 304 to the engine, preventing or reducing engineoverspeed.

Excess hydraulic fluid goes through the relief valve 324 to the low sideof the loop. This minimizes heat generation in the system.

In use, if the engine dies at machine high velocity on flat ground or ifthe engine dies when the machine travels downhill, the braking energyprovides pressurized hydraulic fluid from the high-pressure port B ofthe motor 312 for emergency steering and/or braking while charging theaccumulator(s) at the same time.

An orifice 322 and the relief valve 324 determine how much of thebraking power is converted to heat, with the rest being the input powerfrom the pump 304 to the engine if the valve 332 gets stuck in ablocking position.

It should be appreciated that the hydrostatic braking power of themachine is not negatively influenced by the features of the presentdisclosure. During use, the motor 312 always records the maximum brakingpressure as if the features don't exist. Only the fan motor 346, thecheck valve 344 and the 4-way valve 348 are exposed to the maximumbraking pressure during engine dynamic braking. As such, they should berated to the maximum braking pressure. The braking energy may also makethe fan motor 346 run faster than normal speed. Accordingly, the systemdesign should account for the fan motor 346 maximum speed to remainwithin its limits when subjected to maximum braking pressure.

When the machine travels in reverse direction, the solenoid valve 320 isenergized and the valve 338 is de-energized. Port B is high pressure.During this operation, the port B between the pump 304 and the motor 312is connected. Port B is blocked from fan drive motor 346 and from theaccumulator 356 after the accumulator 356 is fully charged to thepressure-reducing valve 336 setting.

When the machine accelerates in a forward direction, the solenoid valve320 is energized and the valve 338 is de-energized. Port B is lowpressure and is connected between the pump 304 and the motor 312. Theport B is blocked from accumulator 356 and fan drive motor 346. If themachine does not have sufficient horse power to accelerate, or if anacceleration boost is desired, port A pressure drops to below a certainvalue (e.g., 200 bar or any other value), the micro-controller (notshown) receives a signal from the pressure transducer 326 and energizesthe solenoid valve 354, the accumulator 356 discharges energy to assistacceleration until it is fully discharged, then the solenoid valve 354is de-energized.

When the machine is being towed in a forward direction, the motor 312runs as a pump. The high pressure at port B shifts hydraulicpilot-operated valves 330 and 332. Port A and port B of the motor 312are connected when the solenoid valve 354 is manually overridden. Thetowing is unlimited because the pump 304 is bypassed.

If the accumulator(s) 356 is fully charged before the towing, thesteering function can be run to discharge the accumulator(s) 356. Thesteering is limited because the return hydraulic fluid from the steeringis draining out of the loop. It may cause damage to the pump 304 andmotor 312 when there is not sufficient hydraulic fluid in the loop. Inany case, there typically is not much need for steering during towingand this will not affect the unlimited towing.

It should be appreciated that the accumulator 356, as illustrated inFIGS. 3A and 3B, is shown as being included with a charging system.However, such a configuration is non-limiting. For example, theaccumulator could also be provided as a standalone component. Moreover,the accumulator 356 in FIGS. 3A and 3B is illustrated as part of acharging system with one or more fixed pumps. However, this isnon-limiting, and it should be understood that the charging system andaccumulator could also utilize one or more variable pumps, or acombination of fixed and variable pumps, without departing from thescope of the present disclosure.

Referring now to FIGS. 4A and 4B, an exemplary hydraulic propel system400 in accordance with the present disclosure is shown including ahydraulic fan drive system with an electronic diesel control (“EDC”)pump. FIG. 4B is a simplified version of FIG. 4A, and like referencenumerals have been used to identify identical components. The exemplaryhydraulic propel system 400 includes a hydrostatic pump 404, a mainhydraulic loop 420, and one or more hydrostatic motor(s) 412. The pump404 is connected to the prime motor 402 of a machine or vehicle. Theprime motor drives the pump 404 to deliver hydraulic fluid to the motor412 via supply/return lines 410, 418. A valve 414 inside the pump 404controls the speed and direction of the motor 412 by modulating flowrate and changing flow direction supplied to the motor 412 by the pump404. A charge pump 406 replenishes the main hydraulic loop 420 with cooland clean hydraulic fluid from a sump (reservoir) 422. High-pressurerelief valves 408, 416 provide overpressure protection for the mainhydraulic loop.

In one non-limiting configuration, hydraulic propel system 400 includesa work function circuit 423 configured to minimize engine overspeed(i.e., engine control circuit 423). As illustrated in FIGS. 4A and 4B,the engine control circuit 423 generally includes one or more solenoidvalves 426, 434, orifice 424, relief valve 428, and one or more pressuretransducers 432. However, such a configuration is non-limiting.

In another non-limiting configuration, hydraulic propel system 400 canfurther include work function circuit 435 configured to minimize heatgeneration (i.e., heat control circuit 435). As illustrated in FIGS. 4Aand 4B, the heat control circuit 435 is generally a variabledisplacement pump system that includes fan pump 436, fan drive motor438, and check valve 440. However, such a configuration is non-limiting.

During engine dynamic braking, the micro-controller (not shown) shiftssolenoid valves 426 and 434 and de-strokes the fan pump 436 to 0 degreeswhen pressure transducer 432 measures port B pressure higher than apredetermined value (e.g., 25 bar, etc.). High-pressure relief valves444, 446 provide overpressure protection for the variable fan pumpsystem (i.e., heat control circuit 435). The hydraulic fluid at propelmotor 412 side is directed to the fan motor 438 and 4-way valve 448 onlydue to check valve 440. The return fluid from the fan motor 438 goesback to the port B at propel pump 404 side at a reduced pressure. Theexcessive hydraulic fluid goes through the relief valve 428 to the lowside of the loop. This minimizes heat and input torque from the pump 404to the engine 402.

The orifice 424 and relief valve 428 determine how much of the brakingpower is converted to heat. The remaining braking power is input fromthe pump 404 to the engine 402, but only if solenoid valve 434 fails.

It should be appreciated that the hydrostatic braking power of themachine is not negatively influenced by the features of the presentdisclosure. During use, the motor 412 always records the maximum brakingpressure as if the features don't exist. Only the fan motor 438, the4-way valve 448, and check valve 440 are exposed to the maximum brakingpressure during engine dynamic braking. These components should be ratedto the maximum braking pressure. The braking energy may also make thefan motor 438 run faster than normal speed. Accordingly, system designshould account for the fan motor 438 maximum speed to remain within itslimits when subjected to maximum braking pressure.

Referring now to FIG. 5 , an exemplary hydraulic propel system 500 inaccordance with the present disclosure is shown. System 500 illustratedin FIG. 5 is substantially similar to system 400 illustrated in FIG. 4 .However, system 500 is a fixed pump fan drive system in accordance withthe present disclosure, as opposed to the variable pump system 400. Theexemplary hydraulic propel system 500 includes a hydrostatic pump 504and one or more hydrostatic motor(s) 512. The pump 504 is connected tothe prime motor (not shown) of a machine or vehicle. The prime motordrives the pump 504 to deliver hydraulic fluid from a sump (reservoir)522 to the motor 512 via supply/return lines 510, 518.

In one non-limiting configuration, hydraulic propel system 500 includesa work function circuit 523 configured to minimize engine overspeed(i.e., engine control circuit 523). As illustrated in FIG. 5 , theengine control circuit 523 generally includes one or more solenoidvalves 526, 534, orifice 524, relief valve 528, and one or more pressuretransducers 532. However, such a configuration is non-limiting.

In another non-limiting configuration, hydraulic propel system 500 canfurther include work function circuit 535 configured to minimize heatgeneration (i.e., heat control circuit 535). As illustrated in FIG. 5 ,the heat control circuit 535 is generally a fixed pump system thatincludes fan pump 536, a solenoid valve 538, and a fan drive motor 540.However, such a configuration is non-limiting.

During engine dynamic braking, the micro-controller (not shown) shiftssolenoid valves 526, 534 and dumps fan pump 536 to reservoir 522, viasolenoid valve 538, when pressure transducer 532 measures port Bpressure higher than a predetermined value (e.g., 25 bar, etc.). Highpressure relief valves 544, 546 provide overpressure protection for thefixed fan pump system (i.e., heat control circuit 535). The hydraulicfluid at propel motor 512 side is directed to the fan motor 540 and4-way valve 548 only due to check valve 542. The return hydraulic fluidfrom fan motor 540 goes back to port B at propel pump 504 side at areduced pressure. The excessive hydraulic fluid goes through the reliefvalve 528 to the low side of the loop. This minimizes heat and inputtorque from the pump 504 to the engine.

The orifice 524 and relief valve 528 determine how much of the brakingpower is converted to heat. The remaining braking power is input fromthe pump 504 to the engine if the valve 534 gets stuck in blockingposition.

It should be appreciated that the hydrostatic braking power of themachine is not negatively influenced by the features of the presentdisclosure. During use, the motor 512 always records the maximum brakingpressure as if the features don't exist. Only the fan motor 538, the4-way valve 548, and check valve 542 are exposed to the maximum brakingpressure during engine dynamic braking. They should be rated to themaximum braking pressure. The braking energy may also make the fan motor538 run faster than normal speed. Accordingly, system design shouldaccount for the fan motor 438 maximum speed to remain within its limitswhen subjected to maximum braking pressure.

Referring now to FIGS. 6A and 6B, there is illustrated a non-limitingexemplary embodiment of hydraulic circuit 600 in accordance with aspectsof the present disclosure. In this embodiment, braking energy isutilized for an accumulator charging system and emergency steering andbraking. More particularly, circuit 600 includes one or more dedicatedwork function circuits configured perform the aforementioned tasks. Inone non-limiting configuration, hydraulic circuit 600 includes a workfunction circuit 619 configured to minimize engine overspeed, assist inacceleration, and permit unlimited towing (i.e., engine control circuit619). As illustrated in FIG. 6A, the engine control circuit 619generally includes one or more solenoid valves 620, 638, orifice 622,relief valve 624, one or more pressure transducers 626, 628, check valve634, and pressure-reducing valve 636. However, such a configuration isnon-limiting.

In another non-limiting configuration, hydraulic circuit 600 can alsoinclude a braking energy circuit 649 configured to control emergencysteering and braking as well as accumulator(s) charging. As illustratedin FIG. 6B, the braking energy circuit 649 generally includes steeringcontrol circuit 650, braking control circuit 652, solenoid valve 654,accumulator(s) 656, and hydraulic valve manifold 658. However, such aconfiguration is non-limiting. The steering control circuit 650 andbraking control circuit 652 can optionally include one or more fixedand/or variable pumps. The hydraulic valve manifold 658 of the brakingenergy circuit 649 typically includes any number of different types ofhydraulic valves and/or solenoid valves which can be configured todirect the braking energy to each of the dedicated work functions, suchas charging accumulator(s) 656, enabling steering and braking by controlcircuits 650/652, and/or enabling engine control circuit 619. However,such a configuration is non-limiting.

Moreover, the hydraulic circuit 600 and each of the dedicated workfunction circuits (e.g., engine control circuit 619 and braking energycircuit 649) include valving (shown but not numbered) which is generallyoperative to direct at least a portion of pressurized fluid output fromthe motor during braking operations to at least one of the one or morework function circuits or accumulators. It should also be appreciatedthat other types of work functions can additionally or alternatively bepowered by the braking energy without departing from the scope of thisdisclosure.

The exemplary hydraulic circuit 600 illustrated in FIGS. 6A and 6B isadvantageously enabled to respond to various states of machineoperation. For example, exemplary hydraulic circuit 600 may operate inresponse to machine operation states such as: when the engine dies athigh machine velocity on flat ground; when the engine dies while themachine travels downhill; during machine deceleration; when the machineis being towed; and/or any other situation when motor 612 is running asa pump and the pump 604 is running as a motor. During these situations,port B pressure goes up, and port A pressure goes down.

During operation of exemplary hydraulic circuit 600 (i.e., duringdynamic engine braking) the pressure-reducing valve 636 settingdetermines the pressure to which the accumulator 656 is charged. Whenthe accumulator 656 is fully charged, the micro-controller (not shown)receives a signal from the pressure transducer 628 and shifts solenoidvalves 620 and 638. The signal can report that port B pressure is higherthan a set value (e.g., 25 bar). By blocking port B between the pump 604and the motor 612, the braking energy from high-pressure port B at themotor 612 side is transferred to the various other work functions (e.g.,transferred to run steering, braking, charging accumulator(s), etc.).

The return hydraulic fluid from the other work function circuits goesback to port B at the pump 604 side and/or the reservoir 660. Thisminimizes input torque from the pump 604 to the engine, preventing orreducing engine overspeed. Excess hydraulic fluid goes through therelief valve 624 to the low side of the loop. This minimizes heatgeneration in the system. In use, if the engine dies at machine highvelocity on flat ground or if the engine dies when the machine travelsdownhill, the braking energy provides pressurized hydraulic fluid fromthe high-pressure port B of the motor 612 for emergency steering and/orbraking while charging the accumulator(s) 656 at the same time.

An orifice 622 and the relief valve 624 determine how much of thebraking power is converted to heat, with the rest being the input powerfrom the pump 604 to the engine if the valve 638 gets stuck in blockingposition.

When the machine travels in reverse direction, the solenoid valve 620 isenergized and the valve 638 is de-energized. Port B is high pressure andis connected between the pump 604 and the motor 612. Port B is blockedfrom the accumulator 656 after the accumulator 656 is fully charged tothe pressure reducing valve 636 setting.

When the machine accelerates in forward direction, the solenoid valve620 is energized and the valve 638 is de-energized. Port B is lowpressure and it connected between the pump 604 and the motor 612. Port Bis blocked from accumulator 656. If the machine does not have sufficienthorse power to accelerate, or if acceleration boost is desired, port Apressure drops to below a predetermined value (e.g., 200 bar or anyother value), the micro-controller (not shown) receives a signal fromthe pressure transducer 626 and energizes the solenoid valve 654, theaccumulator 656 discharges energy to assist acceleration until it isfully discharged, then the solenoid valve 654 is de-energized.

When the machine is being towed in forward direction, the motor 612 runsas a pump. The high pressure at port B shifts solenoid valves 620 and638. Port A and port B of the motor 612 is connected when the solenoidvalve 654 is manually overridden. The towing is unlimited because thepump 604 is bypassed.

If the accumulator(s) 656 is fully charged before the towing, thesteering function can be run to discharge the accumulator(s) 656. Thesteering is limited because the return hydraulic fluid from the steeringis draining out of the loop. It may cause damage to the pump 604 andmotor 612 when there is not sufficient hydraulic fluid in the loop. Inany case, there typically is not much need for steering during towingand this will not affect the unlimited towing.

It should be appreciated that the accumulator 656, as illustrated inFIGS. 6A and 6B, is shown as being included with a charging system.However, such a configuration is non-limiting. For example, theaccumulator could also be provided as a standalone component. Moreover,the accumulator 656 in FIGS. 6A and 6B is illustrated as part of acharging system with one or more fixed pumps. However, this isnon-limiting, and it should be understood that the charging system andaccumulator could also utilize one or more variable pumps, or acombination of fixed and variable pumps, without departing from thescope of the present disclosure.

It should now be appreciated that, in view of the various non-limitingembodiments discussed above, one or more of the following features maybe present in a hydraulic circuit according to the system and methoddisclosed herein. The exemplary propel systems can be hydrostaticsystems or open-circuit systems. The hydrostatic propel systems can be1x pump and 1x motor, 1x pump and more motors, or any numbers of pumpsand motors, and the motor(s) can be fixed, 2-position or proportional.The open-circuit propel system can be 1x pump and 1x motor, 1x pump andmore motors, or any numbers of pumps and motors, and the motor(s) can befixed, 2-position or proportional.

While considerable emphasis has been placed herein on the structures andconfigurations of the preferred embodiments of the disclosure, it willbe appreciated that other embodiments, as well as modifications of theembodiments disclosed herein, can be made without departing from theprinciples of the disclosure. These and other modifications of thepreferred embodiments, as well as other embodiments of the disclosure,will be obvious and suggested to those skilled in the art from thedisclosure herein, whereby it is to be distinctly understood that theforegoing descriptive matter is to be interpreted merely as illustrativeof the present disclosure and not as a limitation thereof.

1-20. (canceled)
 21. A hydraulic circuit comprising: a pump configuredto be driven by a prime motor; a secondary motor fluidly coupled to saidpump by a supply line and a return line; said secondary motor includinga high-pressure port side; a fluid output from said secondary motor; afirst work function circuit fluidly coupled to said supply line and saidreturn line; said first work function circuit includes a first workfunction actuator and an engine control circuit; said engine controlcircuit configured to a) minimize overspeeding of said prime motor,and/or b) assist in acceleration of said secondary motor; said firstwork function actuator selected from the group consisting of: a) a fandrive motor, b) a generator motor, c) a cylinder, d) a rotary actuator,e) a work function motor, and f) an actuator motor that is loaded duringdynamic engine braking; a heat control circuit configured to reduce heatgeneration; said heat control circuit includes one or more of a fan pumpand a fan heat control motor; and a valving arrangement operative todirect at least a portion of pressurized fluid output from saidsecondary motor during said dynamic engine braking to said heat controlcircuit to reduce or prevent said engine from overspeeding and/or toreduce heat generation in said first work function circuit; said valvingarrangement includes a first pressure valve and a second pressure valve;said first and second pressure valves is configured to be activatedafter a predetermined pressure is sensed; said first and second pressurevalves are configured to facilitate in redirecting at least a portion ofpressurized fluid to said heat control circuit when said first andsecond pressure valves are activated; said valving arrangement includesa first pressure transducer and a pressure reducing valve; said pressurereducing valve includes a preset setting; said pressure reducing valveconfigured to allows fluid to be directed to a fluid accumulator whensaid fluid pressure is at preset setting or exceeds said preset setting;said first pressure transducer is configured to cause at least one ofsaid first and second pressure valves to be activated when said fluidaccumulator is charged at a certain level to thereby direct at least aportion of said fluid to said heat control circuit.
 22. The hydrauliccircuit as defined in claim 21, wherein said first and second pressurevalves are solenoid valves.
 23. The hydraulic circuit as defined inclaim 21, further comprising a second work function circuit; said secondwork function circuit includes one or more of a braking energy circuitthat is configured to control emergency steering and said dynamic enginebraking; said braking energy circuit includes one or more of a steeringcircuit control, a braking circuit control, and a hydraulic valvemanifold.
 24. A method of controlling a hydraulic drive of a machine;said hydraulic drive includes a) a pump adapted to be driven by a primemotor of said machine, b) a secondary motor that is fluidly coupled tosaid pump by a supply line and a return line; said secondary motorincludes a high-pressure port side, and c) a first work function circuitthat is fluidly coupled to said supply line and said return line; saidmethod comprising: directing at least a portion of a pressurized fluidoutput from said high-pressure port side of said motor to a heat controlcircuit; returning said pressurized fluid back to said high-pressureport side of said motor when said secondary motor is running as asecondary pump; activating first and second pressure valves after apredetermined pressure is sensed to facilitate in redirecting saidpressurized fluid to said heat control circuit; and providing a signalfrom a pressure transducer to activate said first and second valves;wherein said directing and returning prevents overspeeding in saidsecondary motor.
 25. The method as defined in claim 24, furthercomprising one or more of: assisting in accelerating said machine;permitting unlimited towing of said machine; and emergency steering andbraking of said machine; wherein one or more of said assisting of saidaccelerating, said permitting of said unlimited towing, and saidemergency steering and braking is at least partially performed by saiddirecting of at least a portion of said pressurized fluid to said firstwork function circuit.
 26. A hydrostatic propulsion system in a machine;said system comprising: a hydraulic circuit; the hydraulic circuitincluding: a pump configured to be driven by a prime motor; a secondarymotor fluidly coupled to said pump by a supply line and a return line;said secondary motor including a high-pressure port side; said secondarymotor is configured to run as a secondary pump; a fluid output from saidsecondary motor; a first work function circuit fluidly coupled with saidsupply line and said return line; said first work function circuitincludes an engine control circuit that is configured to a) minimizeoverspeeding in said prime motor, b) assist in acceleration, and/or c)permit unlimited towing; said first work function circuit includes i) afirst pressure transducer, ii) first and second pilot operated valves,and iii) a pressure reducing valve; said first and second pilot operatedvalves are configured to be activated at a predetermined pressure and toat least partially redirect fluid from said secondary motor and to aheat control circuit; said pressure reducing valve includes a presetsetting said pressure reducing valve configured to allows fluid to bedirected to a fluid accumulator when said fluid pressure is at presetsetting or exceeds said preset setting; said first pressure transduceris configured to cause at least one of said first and second pilotoperated valves to be activated when said fluid accumulator is chargedat a certain level to thereby direct at least a portion of said fluid tosaid heat control circuit; said heat control circuit is configured toreduce heat generation; said heat control circuit includes one or moreof a fan pump and a fan motor, and a valving arrangement operative fordirecting at least a portion of pressurized fluid output from saidsecondary during braking operations to said heat control circuit. 27.The system as defined in claim 26, wherein said heat control circuitfurther includes a solenoid valve, a check valve and a multi-way valve.